The invention relates generally to a stent for use at a bifurcation and, more particularly, a Y-shaped intraluminal vascular stent for repairing bifurcations, the aorto-ostium, and bifurcated blood vessels that are diseased.
Stents are conventionally used for revascularization or re-establishment of blood flow through vessels. Stents are generally hollow and cylindrical in shape and have terminal ends that are generally perpendicular to their longitudinal axes. In use, the conventional stent is positioned at the diseased area of a vessel and, after placement, the stent provides an unobstructed pathway for blood flow.
Re-establishing blood flow through diseased vessels at a bifurcation is particularly challenging since the stent must overlay the entire diseased area at the bifurcation, yet not itself compromise blood flow. Therefore, the stent must, without compromising blood flow, provide adequate coverage by overlaying the entire circumference of the ostium to a diseased portion and extend to a point within and beyond the diseased portion. When the stent does not provide adequate coverage, then potential failure can occur by allowing disease to prolapse into the vessel lumen. When the stent overlays the entire circumference of the ostium to the diseased portion, yet extends into the junction comprising the bifurcation, the diseased area is repaired, but blood flow may be compromised in other portions of the bifurcation. Unapposed stent elements may promote lumen compromise during neointimalization and healing, producing restenosis and requiring further procedures. Moreover, by extending into the junction comprising the bifurcation, the stent may block access to portions of the bifurcated vessel that require performance of further interventional procedures. Similar problems are encountered when vessels are diseased at their angled origin from the aorta as in the ostium of a right coronary or a vein graft. In this circumstance, a stent overlying the entire circumference of the ostium extends back into the aorta, creating problems, including those for repeat catheter access to the vessel involved in further interventional procedures.
Conventional stents are designed to re-establish blood flow in vessels that are removed from bifurcations and, since conventional stents generally terminate at right angles to their longitudinal axes, the use of conventional stents in the region of a vessel bifurcation may result in blocking blood flow of a side branch or fail to repair the bifurcation to the fullest extent necessary. The conventional stent might be placed so that a portion of the stent extends into the pathway of blood flow to a side branch of the bifurcation or extends so far as to completely cover the path of blood flow in a side branch. The conventional stent might alternatively be placed proximal to, but not entirely overlaying the circumference of the ostium to the diseased portion. Such a position of the conventional stent can result in a bifurcation that is not completely repaired or can compromise blood flow into areas or origins requiring blood for proper function.
The only conceivable situation in which the conventional stent, having right-angled terminal ends, could be placed where the entire circumference of the ostium is repaired without compromising blood flow, is where the bifurcation is formed of right angles. In such scenarios, extremely precise positioning of the conventional stent is required. This extremely precise positioning of the conventional stent may result in the right-angled terminal ends of the conventional stent overlying the entire circumference of the ostium to the diseased portion without extending into a side branch, thereby completely repairing the right-angled bifurcation.
To circumvent or overcome the problems and limitations associated with conventional stents in the context of repairing diseased bifurcated vessels, a stent that consistently overlays the entire circumference of the ostium to a diseased portion, yet does not extend into the junction comprising the bifurcation, may be employed. Such a stent would have the advantage of completely repairing the vessel at the bifurcation without obstructing blood flow in other portions of the bifurcation. In addition, such a stent would allow access to all portions of the bifurcated vessel should further interventional treatment be necessary. In a situation involving disease in the origin of an angulated aorto-ostial vessel, such a stent would have the advantage of completely repairing the vessel origin without protruding into the aorta or complicating repeat access.
In addition to the problems encountered by using the prior art stents to treat bifurcations, the delivery platform for implanting such stents has presented numerous problems. For example, a conventional stent is implanted in the main vessel so that a portion of the stent is across the side branch, so that stenting of the side branch must occur through the main-vessel stent struts. In this method, commonly referred to in the art as the xe2x80x9cmonoclonal antibodyxe2x80x9d approach, the main-vessel stent struts must be spread apart to form an opening to the side-branch vessel and then a catheter with a stent is delivered through the opening. The cell to be spread apart must be randomly and blindly selected by recrossing the deployed stent with a wire. The drawback with this approach is there is no way to determine or guarantee that the main-vessel stent struts are properly oriented with respect to the side branch or that the appropriate cell has been selected by the wire for dilatation. The aperture created often does not provide a clear opening and creates a major distortion in the surrounding stent struts. The drawback with this approach is that there is no way to tell if the main-vessel stent struts have been properly oriented and spread apart to provide a clear opening for stenting the side-branch vessel.
In another prior art method for treating bifurcated vessels, commonly referred to as the xe2x80x9cCulotte technique,xe2x80x9d the side-branch vessel is first stented so that the stent protrudes into the main vessel. A dilatation is then performed in the main vessel to open and stretch the stent struts extending across the lumen from the side-branch vessel. Thereafter, the main-vessel stent is implanted so that its proximal end overlaps with the side-branch vessel. One of the drawbacks of this approach is that the orientation of the stent elements protruding from the side-branch vessel into the main vessel is completely random. Furthermore the deployed stent must be recrossed with a wire blindly and arbitrarily selecting a particular stent cell. When dilating the main-vessel stent, stretching the stent struts is therefore random, leaving the possibility of restricted access, incomplete lumen dilatation, and major stent distortion. Furthermore, this technique is rapidly falling into disfavor due to the excess metal that must be placed within the parent or proximal vessel.
In another prior art device and method of implanting stents, a xe2x80x9cTxe2x80x9d stent procedure includes implanting a stent in the side-branch ostium of the bifurcation followed by stenting the main vessel across the side-branch ostium. In another prior art procedure, known as xe2x80x9ckissingxe2x80x9d stents, a stent is implanted in the main vessel with a side-branch stent partially extending into the main vessel creating a double-barrelled lumen of the two stents in the main vessel proximate the bifurcation. Another prior art approach includes a so-called xe2x80x9ctrouser legs and seatxe2x80x9d approach, which includes implanting three stents, one stent in the side-branch vessel, a second stent in a distal portion of the main vessel, and a third stent, or a proximal stent, in the main vessel proximate the bifurcation.
All of the foregoing stent deployment assemblies suffer from the same problems and limitations. Typically, there are uncovered intimal surface segments on the main vessel and side-branch vessels between the stented segments. An uncovered flap or fold in the intima or plaque will invite a xe2x80x9csnowplowxe2x80x9d effect, representing a substantial risk for subacute thrombosis, and the increased risk of the development of restenosis. Further, where portions of the stent are left unapposed within the lumen, the risk for subacute thrombosis or the development of restenosis again is increased. The prior art stents and delivery assemblies for treating bifurcations are difficult to use, making successful placement nearly impossible. Further, even where placement has been successful, the side-branch vessel can be xe2x80x9cjailedxe2x80x9d or covered so that there is impaired access to the stented area for subsequent intervention.
Previous attempts have been made to produce bifurcated stents, or Y-shaped stents, for treating arterial bifurcations. Typically, these prior art stents are difficult to manufacture. Moreover, these prior art stents are often bulky making them difficult to deliver and precisely place at the carina of the vessel. Moreover, these stents often lack sufficient scaffolding at the carina and other areas to properly cover existing disease within the vessel. The present invention solves these and other problems as will be shown.
What has been needed and heretofore unavailable is an improved Y-shaped stent that can be used to effectively treat arterial bifurcations. It is also desirable that such a Y-shaped stent be easy to use and precisely place, relatively inexpensive to manufacture, and constructed from materials that are common in the industry today. The present invention satisfies these needs.
The present invention is directed to an improved Y-shaped stent design for repairing a main vessel and side-branch vessel forming a bifurcation. The stent may easily be placed with precision at a bifurcation to effectively treat a diseased area. Moreover, the manufacturing process has been simplified.
In one aspect of the invention there is provided a longitudinally flexible Y-shaped stent for implanting in a bifurcated body lumen that includes a first generally cylindrical distal branch defining a first flow path for fluid flow and second generally cylindrical distal branch defining a second flow path for fluid flow. The first and second distal branches are interconnected by one or more bending elements at a carina junction. Each of the bending elements are flexible such that the first and second distal branches are capable of pivoting about the bending elements at the carina junction, thus defining an angle of varying degree such that the carina junction extends proximal the proximal end of the first and second distal branches.
The Y-shaped stent further includes a generally cylindrical proximal branch defining a third flow path for fluid flow. The proximal branch is attached to the first and second distal branches proximal the carina junction such that the first and second distal branches and the proximal branch are in communication with each other. During delivery of the Y-shaped stent in the bifurcated lumen, the carina junction comes into apposition with the carina of the body lumen so that the Y-shaped stent can no longer be advanced distally, which facilitates precise placement of the Y-shaped stent in the bifurcated lumen.
In another aspect of the invention there is provided a longitudinally flexible Y-shaped stent for implanting in a bifurcated body lumen and expandable from contracted condition to an expanded condition. The Y-shaped stent includes a plurality of adjacent cylindrical elements each having a circumference extending around a longitudinal stent axis and each element being substantially independently expandable in the radial direction, the cylindrical elements being arranged in alignment along the longitudinal stent axis. The cylindrical elements are formed in a generally serpentine wave pattern transverse to the longitudinal axis and contain a plurality of alternating peaks and valleys. The peaks on each of the cylindrical elements are substantially aligned in phase along the longitudinal stent axis. At least one interconnecting member extends between adjacent cylindrical elements and connects them to one another to form the longitudinally flexible Y-shaped stent.
The Y-shaped stent has a proximal end and a distal end in communication with each other, the proximal end including a generally cylindrical proximal branch and the distal end including a first generally cylindrical distal branch and a second generally cylindrical distal branch. The first and second distal branches and the proximal branch are in communication with each other.
In yet another aspect of the invention there is provided a longitudinally flexible Y-shaped stent for implanting in a bifurcated body lumen, including a plurality of cylindrical elements that are independently expandable in the radial direction and that are interconnected so as to be generally aligned on a common longitudinal axis. The Y-shaped stent further includes a plurality of connecting elements for interconnecting the cylindrical elements. The connecting elements are configured to interconnect only the cylindrical elements that are adjacent to each other. There is an outer wall surface on the cylindrical elements, the outer wall surface being smooth prior to expansion of the Y-shaped stent and forming a plurality of outwardly projecting edges that form as the stent is expanded radially outwardly from a first diameter to a second, enlarged diameter.
Similarly, this Y-shaped stent also has a proximal end and a distal end in communication with each other, the proximal end including a generally cylindrical proximal branch and the distal end including a first generally cylindrical distal branch and a second generally cylindrical distal branch. The first and second distal branches and the proximal branch are in communication with each other.
In a still further aspect of the invention there is provided a method of making an expandable metal Y-shaped stent, including the step of forming a proximal stent section out of a first metal tube and a distal stent section out of a second metal tube, the distal stent section having a first distal branch and a second distal branch. The first distal branch and the second distal branch are connected by bending elements, thereby forming a carina junction. Male struts and female struts are cut into the first tube and the second tube such that decreasing the angle between the distal branches serves to cause the male and female struts cut into the second tube to assume a position to facilitate attachment.
In another aspect of the invention there is provided a longitudinally flexible Y-shaped stent for implanting in a bifurcated body lumen, including a first stent section having a first main portion and a first hinged portion, the first hinged portion being hingedly attached to the first main portion such that the first stent section has an open configuration and a closed configuration. A second stent section has a second main portion and a second hinged portion, the second hinged portion being hingedly attached to the second main portion such that the second stent section has an open configuration and a closed configuration.
The first stent section may be mated with the second stent section while the first stent section and the second stent section are in open configurations. Once mated, the first stent section together with the second stent section create a combination having a proximal end and a distal end in communication with each other. The proximal end includes a generally cylindrical proximal branch, and the distal end includes a first generally cylindrical distal branch and a second generally cylindrical distal branch. The first and second distal branches and the proximal branch are in communication with each other.
In another aspect there is provided a method of making an expandable metal Y-shaped stent, including the step of forming a first stent section out of a first metal tube and a second stent section out of a second metal tube. The first stent section has a first main portion and a first hinged portion hingedly attached to the first main portion such that the first stent section has an open configuration and a closed configuration. The second stent section has a second main portion and a second hinged portion hingedly attached to the second main portion such that the second stent section has an open configuration and a closed configuration.